Pressure ulcers are formed when one or more parts of the body are subjected to prolonged pressure. Pressure ulcers and related medical conditions such as pressure induced ischemia are a serious health hazard for patients who are prone to stay in the same or substantially the same posture in bed/chair or any other surface for an extended amount of time subjecting parts of their bodies to sustained pressure. These pressure ulcers, if left undetected, can potentially cause infection that may be life threatening, and complicated and expensive to treat. Besides the human costs, the economic loss is in billions of dollars for USA alone. It is therefore imperative to find much more effective solutions to help prevent pressure ulcers.
The current prevalent method for preventing Pressure Ulcers is largely manual in that patients change their position through their own efforts or with help from the caregiver at periodic intervals. For example, the current guidelines recommend that patients be turned every two hours by default. However, this method has not worked well in practice as busy caregivers often forget to turn the patient. Also, sometimes the patient may inadvertently revert to a position which could cause harm. In order to improve this prevention process, several solutions have been suggested and offered on the market.
The solutions that have been proposed and/or built fall into two distinct classes. At the outset, it is important to point out that prior art for both classes of system uses simple pressure sensing units that have no inbuilt intelligence. The first class of solutions attempt to estimate the pressure on the various body parts or limbs indirectly. These methods as described in U.S. Patent No. 2013/0090571 include measuring the pressure at various points on the mattress where the patient is lying. From this pressure map, the system attempts to guess the body parts that cause that pressure and its magnitude. Since the patient may move around in the bed, it can be difficult to ascertain if the pressure at any given area of the mattress is still being caused by the same body part. Using these methods, accurately estimating the impact of pressure on specific body parts has proved to be difficult in practice, involves complex computations and expensive to implement & deploy. There have been several proposals to improve upon this process by use of camera and/or other locationing technologies to augment the determination of patient position, International Patent No. WO2015054423 but they all suffer from additional complexities without adequately solving the inherent issue of measuring the pressure at various body parts accurately. Yet other solutions employ turn indicator to record and report if the patient has been turned. Since the turn indicator is typically mounted in a chest area, it does not measure the pressure at all but more geared towards enforcing the manual turn policies.
The second class of solutions attempt to measure pressure directly at the body parts/limbs by use of patches that contain a pressure sensor. U.S. Pat. No. 6,287,253 describes the use of a transducer based pressure sensor that can be applied to human body. This pressure sensor detects either presence and absence of a preset pressure threshold on the various points of the body which is then read by a nearby transmitter-receiver system using a frequency resonant method. The status of pressure on/off is read periodically via polling and sent it to their controller for reporting purposes. There are several important differences between the systems described in U.S. Pat. No. 6,287,253 and the invention described here which have profound impact on the utility and effectiveness of the overall system.
First, their invention's primary focus is the design of the pressure sensor and enable its reading via a resonant frequency to nearby readers. There are several limitations to their system. Each of their sensors need to be preset to specific pressures on/off thresholds based on the location on the body. This poses an suitability issue as the risk of forming an ulcer is a function of the amount of pressure applied over time. If the amount of pressure exerted is highly approximate (present/not present) then it impacts the ability of the system to assess risks accurately. The resonant frequency technology used for communicating this pressure on/off information may be limited in its range and may pose difficulties when the patient is lying on top of the sensor. Lack of intelligence in the pressure sensor means that the sensing unit may not have software configurable thresholds, may not easily adapt to the needs of different patients, may not support a local decision engine, generate local alarms or support two way communication. The lack of intelligence in the sensor also implies that system configurability is difficult and may have to be supported at the time of manufacturing while scalability of the system is limited as each pressure sensor needs to be tuned to a different frequency along with possible corresponding changes in transmitters & receivers used to read them. The standalone pressure sensor in absence of intelligent architecture is also not extensible as it does not support other sensors in an integrated manner required for improved patient monitoring. Finally, deployability of such a system may be difficult if multiple transmitters/receivers per patient are required.